Correlation of the Silurian of Bohemia. 69 



Correlation of Bohemian Strata. 



A detailed and definite parallelization of Silurian strata 

 in Bohemia with those in foreign countries can not yet be 

 made, therefore only a scheme of approximate correlation 

 is inserted here, based chiefly on the geological distribu- 

 tion of gr apt otitic and other faunas and on the zones con- 

 nected therewith. Further investigations in Barrande's 

 area will surely reveal many important details and solve 

 questions either merely mentioned or omitted in the pres- 

 ent connnunication ; moreover, future progress in zonal 

 division and correlation in other countries will also 

 modify the scheme here given. Because of limited space, 

 two or three smaller districts of the chief countries are 

 combined in single columns. The greatest changes will 

 probably take place when future investigations are made 

 with due regard to the principles, facts, and views dis- 

 cussed in Ulrica's "Revision of the Paleozoic systems." 23 



To the scheme above, in which only the "normal" 

 shaly facies and not the aberrant reef deposits are con- 

 cerned, a few remarks can now be added. There is in the 

 main divisions and succession of faunas in Bohemia a 

 general harmony with those of other countries; in par- 

 ticular, Eja, E^, and E^/ correspond well enough with 

 the Rastrites-, Cyrtograptus-, and col onus -shales in 

 Sweden. But in the subordinate zones, there are consider- 

 able differences in their vertical limits, a feature not sur- 

 prising when we consider the great geographic separation 

 of the Bohemian basin and the varied development of its 

 deposits (see for instance, the relative frequency of grap- 

 tolites in limestones in association with various molluscs 

 and brachiopods). The higher the zones, the greater the 

 differences; this seems to be partly due to the fact, 

 observed in graptolitic faunas in Great Britain by Miss 

 E. M. R. "Wood, that graptolites of the highest Silurian 

 zones show an extended vertical range and limited geo- 

 graphic distribution. There seem to be considerable dif- 

 ferences in the association of some graptolites in the 

 higher Bohemian zones, as compared with those of "Wen- 



23 Bull. Geol. Soc. America, 22, 1911. I confess freely that Ulrich's work 

 made so strong an impression upon me that I hesitated to publish the present 

 communication and was about to review all my former studies from the 

 standpoints of that work. This would, however, cause another considerable 

 delay, so that I preferred to print the present article (cf. footnote 6), the 

 purpose of which is to offer at once a general orientation to foreign students. 



